In a conventional liquid crystal display (LCD) panel, a fringe field switching (FFS) technology has been generally employed to widen the viewing angle of the LCD panel. The FFS technology provides the LCD panel with a wide viewing angle, in which technology both a common electrode and a pixel electrode are formed on an array substrate and a fringe electric field formed between the electrodes is used to drive the liquid crystal. Such FFS LCD panel has the advantages of a wide viewing angle, less color bias, lower power consumption, etc. In addition, in order to further enhance display performance, the conventional FFS technology may also employ a multi-domain design in a single pixel.
FIGS. 1 and 2 are schematic views of a single domain sub-pixel array unit and a double domain sub-pixel array unit based on the FFS technology, respectively. The whole display area of the LCD panel is formed by combining a plurality of pixels of the same configuration. Specifically, the direction of the oblique lines in the figures represents the inclination direction of the corresponding pixel electrodes. Each pixel comprises three sub-pixels, i.e., red, green, and blue sub-pixels. In FIG. 1, a red sub-pixel 11, a green sub-pixel 12, and a blue sub-pixel 13 in a pixel 10 are all single domain sub-pixels, i.e., the inclination directions of the pixel electrodes of each sub-pixel are identical with each other. In FIG. 2, a red sub-pixel 21, a green sub-pixel 22, and a blue sub-pixel 23 in a pixel 20 are all double domain sub-pixels, i.e., each sub-pixel has two inclination directions of the pixel electrodes. In FIG. 2, the upper portion of each sub-pixel employs a symmetry configuration with respect to the lower portion.
The defects of the conventional design lies in that the single domain sub-pixel shown in FIG. 1 has a larger color bias and a poorer viewing angle compared with the double domain sub-pixel shown in FIG. 2. The specific experimental data are shown in FIGS. 3-6, which illustrate comparison views of the color bias and the viewing angle for two types of pixel, respectively. It can be seen from the figures that the single domain sub-pixel generates larger color bias as the viewing angle changes, and the viewing angles in the horizontal and vertical directions have a relatively poor effect.
The double domain sub-pixel shown in FIG. 2 has a better color bias effect and a better viewing angle effect. However, in the boundary area between the upper portion and the lower portion of the pixel as shown with the black triangles in FIG. 2, the inclination directions of the pixel electrodes are opposite to each other, i.e., there are two different liquid crystal domains in the apertures area of a single pixel. Therefore, it is difficult for the electric field of the pixel electrodes to drive the LCD panel effectively, resulting in that the optical efficiency of the liquid crystal in the boundary area is extremely low and lowering the light transmissivity for the whole LCD panel. In addition, when the applied electrical filed is extremely large, the boundary area between the two domains may also expand into the normal display areas, which imposes a bigger influence on the display performance of the product.
In the conventional technology, in order to overcome the defect of the low light transmissivity of the above double domain sub-pixel, a normally used method is to enhance the power of a backlight source. However, it means a higher cost requirement and higher power consumption, but the effect is not satisfactory.